Charged particle beam writing apparatus, and buffer memory data storage method

ABSTRACT

A charged particle beam writing apparatus includes a buffer memory including a memory region capable of contemporarily storing writing data for data processing regions, wherein writing data including data files is temporarily stored for each of the data processing regions, a dividing unit to divide the memory region of the buffer memory into a first region being large and a second region being small, a specifying unit to specify the memory region such that a data file being large is preferentially stored in the first region and a data file being small is stored at least in the second region, concerning the data files for each of the data processing regions included in the writing data, and a data processing unit to read data files corresponding to each of the data processing regions from the buffer memory, and to perform data processing using the read data files.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2013-028504 filed on Feb. 18,2013 in Japan, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a charged particle beam writingapparatus and a buffer memory data storage method. More specifically,for example, the present invention relates to a writing apparatus thatperforms data processing for each processing region by inputting writingdata into a buffer memory, and a method therefor.

Description of Related Art

The lithography technique that advances miniaturization of semiconductordevices is extremely important as being a unique process wherebypatterns are formed in semiconductor manufacturing. In recent years,with high integration of LSI, the line width (critical dimension)required for semiconductor device circuits is decreasing year by year.For forming a desired circuit pattern on such semiconductor devices, amaster or “original” pattern (also called a mask or a reticle) of highaccuracy is needed. Thus, the electron beam (EB) writing technique,which intrinsically has excellent resolution, is used for producing sucha high-precision master pattern.

FIG. 9 is a conceptual diagram for explaining operations of a variableshaped electron beam writing or “drawing” apparatus. As shown in thefigure, the variable shaped electron beam writing apparatus operates asdescribed below. A first aperture 410 has a quadrangular opening 411 forshaping an electron beam 330. A second aperture 420 has a variable-shapeopening 421 for shaping the electron beam 330 having passed through theopening 411 of the first aperture 410 into a desired quadrangular shape.The electron beam 330 emitted from a charged particle source 430 andhaving passed through the opening 411 is deflected by a deflector topass through a part of the variable-shape opening 421 of the secondaperture 420, and thereby to irradiate a target object or “sample” 340placed on a stage which continuously moves in one predetermineddirection (e.g., the x direction) during the writing. In other words, aquadrangular shape that can pass through both the opening 411 and thevariable-shape opening 421 is used for pattern writing in a writingregion of the target object 340 on the stage continuously moving in thex direction. This method of forming a given shape by letting beams passthrough both the opening 411 of the first aperture 410 and thevariable-shape opening 421 of the second aperture 420 is referred to asa variable shaped beam (VSB) system.

When reading writing data in which positions, shapes, etc. of patternsto be written are defined into a memory in a writing apparatus,generally, the data is sorted and stored in a memory region (memoryspace) by a commercial operating system (OS) that controls the controlcomputer. Then, in the processing side wherein data processing isperformed, data is read from the memory and conversion of the data isperformed to generate data required for writing processing. In thewriting apparatus, in parallel with an actual writing operationirradiating electron beams, data processing for a next writingprocessing region is executed in real time. In the system side, when theamount of memory used exceeds a specified amount, data not being used atthe time is deleted from the memory by a garbage collection functionperformed by the OS. Then, next data is sequentially stored in an emptyregion. In recent years, the number of patterns written is increased,and their shapes are various. If data of such patterns is read into thememory by the OS control, fragmentation may occur in the memory.Furthermore, if the memory capacity becomes insufficient, the OSperforms a swap-out by using the hard disk etc.

As described above, when memory control is performed by the OS,fragmentation or swap-out is performed in the memory. This causes aproblem that when data processing is performed in the processing side,the data read-out time becomes long and the data processing speed ofwriting data is deceased. Accordingly, a problem occurs that dataprocessing itself may be stopped in some cases, thereby causing a stopof writing processing.

BRIEF SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, a chargedparticle beam writing apparatus includes a buffer memory configured toinclude a memory region capable of contemporarily storing writing datafor a plurality of data processing regions obtained by virtuallydividing a writing region to be written, wherein writing data includinga plurality of data files is temporarily stored for each of theplurality of data processing regions; a dividing unit configured todivide the memory region of the buffer memory into a first region whoseregion size is large and a second region whose region size is small; aregion specifying unit configured to specify the memory region of thebuffer memory such that a data file whose file size is large haspriority to be stored in the first region and a data file whose filesize is small is stored at least in the second region, with respect tothe plurality of data files for the each of the plurality of dataprocessing regions included in the writing data; a data processing unitconfigured to read the plurality of data files corresponding to the eachof the plurality of data processing regions from the buffer memory, andto perform data processing using the plurality of data files having beenread; and a writing unit configured to write a pattern on a targetobject with charged particle beams, in accordance with content of thedata processing, for the each of the plurality of data processingregions.

In accordance with another aspect of the present invention, a method ofstoring data in a buffer memory includes dividing a memory region of abuffer memory, which can contemporarily store writing data for aplurality of data processing regions obtained by virtually dividing awriting region to be written, wherein writing data including a pluralityof data files is temporarily stored for each of the plurality of dataprocessing regions, into a first region whose region size is large and asecond region whose region size is small; specifying the memory regionof the buffer memory such that a data file whose file size is large haspriority to be stored in the first region and a data file whose filesize is small is stored at least in the second region, with respect tothe plurality of data files for the each of the plurality of dataprocessing regions included in the writing data; and storing, for theeach of the plurality of data processing regions, the plurality of datafiles respectively in a specified memory region in the memory region ofthe buffer memory.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a configuration of a writingapparatus according to the first embodiment;

FIG. 2 shows an example of a chip region and its processing regionaccording to the first embodiment;

FIG. 3 is a flowchart showing main steps of a writing method accordingto the first embodiment;

FIG. 4 is a conceptual diagram showing a memory region of a buffermemory according to the first embodiment;

FIG. 5 is a conceptual diagram showing a memory region of a buffermemory according to the first embodiment;

FIGS. 6A and 6B are conceptual diagrams for explaining a method ofstoring data into a buffer memory according to the first embodiment;

FIG. 7 is an example of a graph showing a relation between an input dataamount and time of a buffer memory according to the first embodiment;

FIG. 8 is a conceptual diagram showing a memory region of a buffermemory according to the second embodiment; and

FIG. 9 is a conceptual diagram for explaining operations of a variableshaped electron beam writing apparatus.

DETAILED DESCRIPTION OF THE INVENTION

In the following embodiments, there will be described a writingapparatus and method that can suppress fragmentation or swapping out ina memory.

Moreover, in the following embodiments, there will be described aconfiguration in which an electron beam is used as an example of acharged particle beam. However, the charged particle beam is not limitedto the electron beam, and other charged particle beam such as an ionbeam may also be used. Moreover, a variable shaped beam type writingapparatus will be described as an example of a charged particle beamapparatus.

First Embodiment

FIG. 1 is a schematic diagram showing the configuration of a writingapparatus according to the first embodiment. In FIG. 1, a writing (or“drawing”) apparatus 100 includes a writing unit 150 and a control unit160. The writing apparatus 100 is an example of a charged particle beamwriting apparatus, and, particularly, it is an example of a variableshaped beam (VSB) type writing apparatus. The writing unit 150 includesan electron lens barrel 102 and a writing chamber 103. In the electronlens barrel 102, there are arranged an electron gun assembly 201, anillumination lens 202, a first aperture 203, a projection lens 204, adeflector 205, a second aperture 206, an objective lens 207, a maindeflector 208, and a sub deflector 209. In the writing chamber 103,there is arranged an XY stage 105, on which a target object or “sample”101 such as a mask serving as a writing target substrate is placed whenperforming writing. The target object 101 is, for example, an exposuremask used for manufacturing semiconductor devices. The target object 101may be, for example, a mask blank on which resist is applied and nopattern has yet been formed.

The control unit 160 includes a control computer 110, a memory 112, abuffer memory 114, a control circuit 130, and storage devices 140 and142, such as magnetic disks. The control computer 110, the memory 112,the buffer memory 114 the control circuit 130, and the storage devices140 and 142 are mutually connected through a bus (not shown).

In the control computer 110, there are arranged a dividing unit 50, aregion specifying unit 52, a determination unit 54, a read unit 56, adetermination unit 57, a deletion unit 58, and a writing data processingunit 59. Each function, such as the dividing unit 50, the regionspecifying unit 52, the determination unit 54 the read unit 56, thedetermination unit 57, the deletion unit 58, and the writing dataprocessing unit 59 may be configured by hardware such as an electroniccircuit or by software such as a program causing a computer to implementthese functions. Alternatively, it may be configured by a combination ofhardware and software. Data which is input and output to/from thedividing unit 50, the region specifying unit 52, the determination unit54 the read unit 56, the determination unit 57, the deletion unit 58,and the writing data processing unit 59 and data being calculated arestored in the memory 112 each time.

FIG. 1 shows a configuration necessary for explaining the firstembodiment. Other configuration elements generally necessary for thewriting apparatus 100 may also be included. For example, although amultiple stage deflector of two stages of the main deflector 208 and thesub deflector 209 is herein used for position deflection, a single stagedeflector or a multiple stage deflector of three or more stages may alsobe used for position deflection.

In the storage device 140 (storage unit), there is stored chip data(writing data) of a chip including a plurality of cells each configuredby at least one figure pattern, input from the outside the apparatus.Each figure pattern data indicating the shape, arrangement coordinatesand size of each figure pattern is defined in the chip data. In otherwords, each figure pattern data indicating the shape, arrangementcoordinates and size of each figure pattern in a chip including aplurality of figure patterns is defined in the chip data.

FIG. 2 shows an example of a chip region and its processing regionaccording to the first embodiment. In FIG. 2, a chip region 10 (writingregion) serving as a writing target is virtually divided into aplurality of frame regions 12 (data processing region). The size of eachframe region 12 may be the same or different from each other as shown inFIG. 2. For example, it is preferable to vary the size of each frameregion 12 according to an amount of data. The writing data describedabove is composed of a plurality of data files for each frame region 12,for example. A cell pattern data file, a position data file, and a linkfile are cited as a plurality of data files of each frame region 12. Itis also preferable to provide a common cell pattern data file separatelywith respect to a cell pattern referred to in a plurality of frameregions 12. In the cell pattern data file, there is defined pattern dataof a cell pattern configured by at least one figure. In the positiondata file, there is defined position data indicating a position(coordinates) of each cell pattern. In the link file, there is definedlink information for linking position data and its corresponding patterndata. Since the cell pattern data file defines the figure type, size,etc. of a figure composing each cell, its data size (amount of data) isvery large compared with the position data file defining coordinates andthe link file defining link information (e.g., an identifier).

In the writing apparatus 100, a plurality of data files corresponding toeach frame region 12 are temporarily stored in the buffer memory 114,for example. Then, in the writing data processing unit 59, data is readfrom the buffer memory 114 and conversion of the data is performed togenerate data required for writing processing. According to the firstembodiment, the memory region (memory space) of the buffer memory 114 isnot controlled by a general commercial operating system (OS) thatcontrols a control computer, but is managed and controlled by aconfiguration arranged specially in the control computer 110.

FIG. 3 is a flowchart showing main steps of a writing method accordingto the first embodiment. In FIG. 3, the writing method according to thefirst embodiment executes a series of steps: a region dividing step(S102), a region specifying step (S104), a determination step (S106), adata read step (S108), a determination step (S109), a data deletion step(S110), a data conversion processing step (S112), and a writing step(S114). In these steps, the region dividing step (S102), the regionspecifying step (S104), the determination step (S106), the data readstep (S108), the determination step (S109), and the data deletion step(S110) are executed as a data storage method of the buffer memoryaccording to the first embodiment.

In the region dividing step (S102), the dividing unit 50 divides thememory region (memory space) of the buffer memory 114 into a large datasize region (first region) whose region size is large and a small datasize region (second region) whose region size is small.

FIG. 4 is a conceptual diagram showing a memory region of a buffermemory according to the first embodiment. As shown in FIG. 4, a memoryregion 20 (memory space) of the buffer memory 114 is divided into two, alarge data size region 22 (A) and a small data size region 24 (B), basedon a dividing position 21. The memory region 20 of the buffer memory 114has a size that can contemporarily store writing data for a plurality offrame regions 12. That is, the memory region 20 has an area for storingdata for a plurality of frame regions 12. It is effectively preferablefor the memory region 20 to have an area for at least three frameregions. It is preferable that a threshold value (the dividing position21) for dividing the memory region 20 into the large data size region 22and the small data size region 24 is determined by using the ratio ofthe file sizes of a plurality of data files. Specifically, first, theratio of the file sizes of the cell pattern data file, the position datafile and the link file is obtained. For example, if the ratio of thesizes of the cell pattern data file, the position data file, and thelink file is 10:1:1, a continuous region of 10/12(ten twelfths) of thememory region 20 is assigned as the large data size region 22, and acontinuous remaining region of 2/12 is assigned as the small data sizeregion 24. In that case, it is preferable that the dividing position 21is adjusted so that a cell pattern data file for at least two frameregions may be stored in the large data size region 22. More preferably,the dividing position 21 is adjusted so that a cell pattern data filefor three frame regions may be stored. For example, the dividingposition 21 obtained based on the ratio of the file sizes of a pluralityof data files may be offset by an amount α with respect to the side ofthe large data size region 22 such that a cell pattern data file for atleast two frame regions is stored. If ratios of the file sizes of aplurality of data files are various depending upon the frame regions 12,it is also preferable to use an average value of the ratios of aplurality of frame regions 12. For example, the average value of ratiosof the file sizes of a plurality of data files for two frame regions maybe used.

In the region specifying step (S104), with respect to writing dataincluding a plurality of data files for each frame region 12, the regionspecifying unit 52 specifies the memory region 20 of the buffer memory114 such that a cell pattern data file whose file size is large is givenpriority to be stored in the large data size region 22 and a positiondata file and a link file whose file sizes are small are stored at leastin the small data size region 24.

In the determination step (S106), the determination unit 54 determineswhether a continuous region whose size is greater than or equal to therequired size can be acquired in a specified region in the buffer memory114. In other words, it is determined whether a continuous empty regionwhose size is greater than or equal to the size necessary for storing aplurality of data files of the frame region 12 concerned can be acquiredin a specified region in the buffer memory 114. If it is impossible toacquire a continuous region greater than or equal to the required size,it proceeds to the data deletion step (S110). If it is possible toacquire a continuous region greater than or equal to the required size,it proceeds to the data read step (S108).

In the data read step (S108), with respect to each frame region 12, theread unit 56 reads and stores a plurality of data files (a cell patterndata file, a position data file, and a link file) respectively to aregion specified in the memory region 20 of the buffer memory 114.

FIG. 5 is a conceptual diagram showing a memory region of a buffermemory according to the first embodiment. In the example of FIG. 5, itstarts to store the cell pattern data file (1) of the first frame region12 from the end side (the opposite side to the dividing position 21side) of the large data size region 22. It also starts to store theposition data file (1) and link file (1) of the first frame region 12from the end side (the opposite side to the dividing position 21 side)of the small data size region 24. It is preferable to store the positiondata file (1) and the link file (1) to be continuous with each other,and the order of storing them is not particularly limited. By the methodof starting storing the files from the end side in order, the storageregion of a subsequent data file can be acquired.

In the determination step (S109), the determination unit 57 determineswhether file data has been stored with respect to all the frame regions12. If storing file data has not been completed with respect to all theframe regions 12, it returns to the region specifying step (S104) andrepeats the steps in order from the region specifying step (S104) to thedetermination step (S109) for subsequent frame regions until storingfile data has been completed with respect to all the frame regions 12.In that case, it should be understood that the data deletion step (S110)described later is also carried out according to the existence ornonexistence of an empty continuous region of the required size in thememory region.

In the example of FIG. 5, the cell pattern data file (1) of the firstframe region 12, the cell pattern data file (2) of the second frameregion 12, and the cell pattern data file (3) of the third frame region12 are stored in order from the end side of the large data size region22. Also, the position data file (1) and link file (1) of the firstframe region 12, the position data file (2) and link file (2) of thesecond frame region 12, and the position data file (3) and link file (3)of the third frame region 12 are stored in order from the end side ofthe small data size region 24.

FIGS. 6A and 6B are shown for explaining a method of storing data intothe buffer memory according to the first embodiment. As a comparativeexample, FIG. 6A shows the case in which the position data file (3) andthe link file (3) of the third frame region 12 are stored in the largedata size region 22 after the data files of the first and second frameregions 12 have been stored. In this case, it is difficult to store thecell pattern data file (3) of the third frame region 12. On the otherhand, according to the first embodiment, it is possible to store thecell pattern data file (3) by the method of storing the position datafile (2) and the link file (2), and further the position data file (3)of the third frame region 12 in order in the small data size region 24commencing from the end side of the region 24 as shown in FIG. 6B. Inthat case, it is acceptable to store the cell pattern data file to beextended over the dividing position 21 to the small data size region 24side from the large data size region 22.

In the data deletion step (S110), if it is impossible to acquire acontinuous region, whose size is greater than or equal to the sizenecessary for storing a plurality of data files of the frame region 12concerned, in a specified region in the buffer memory 114, the deletionunit 58 deletes an unnecessary data file, which has already been used,as needed in order commencing from a frame region 12 that was readearly. For example, when reading the data file for the fourth frameregion 12 in the case of FIG. 5, if a continuous region whose size isgreater than or equal to the required size cannot be acquired due to alack of region, the data file for the first frame region 12 is deletedfirst. If it is still impossible to acquire the continuous region, thedata file for the second frame region 12 is deleted. According to thegarbage collection function performed by a conventional OS, if theremaining amount of the memory is deficient, data for all the frameregions not being used at the time is deleted from the memory. Thereby,it takes an additional time to later re-read a data file which againbecomes necessary. On the other hand, according to the first embodiment,an unnecessary data file which has already been used is deleted asneeded in order commencing from the frame region 12 that was read early.Therefore, it is possible to avoid deleting data files more thannecessary. Thus, the time to re-read a data file can be eliminated orreduced.

In the data conversion processing step (S112), for each frame region 12,the writing data processing unit 59 (data processing unit) reads aplurality of corresponding data files from the buffer memory 114, andperforms data conversion processing (data processing) of a plurality ofsteps by using a plurality of the read data files. Then,apparatus-specific shot data is generated. With regard to a cellpattern, it is usually composed of a plurality of figure patterns. Forwriting a figure pattern by the writing apparatus 100, it needs todivide each figure pattern defined in the cell pattern data to be thesize that can be irradiated by one beam shot. Thus, in order to actuallyperform writing, the writing data processing unit 59 divides each figurepattern into the size that can be irradiated by one beam shot so as togenerate a shot figure. Shot data is generated for each shot figure.Figure data, such as a figure type, figure size, and irradiationposition is defined in the shot data. The generated shot data is storedin the memory 142.

In the writing step (S114), the writing unit 150 writes a pattern on thetarget object 101 in accordance with the content of data having beenprocessed, by using the electron beam 200 for each frame region 12.Specifically, it operates as follows.

The electron beam 200 emitted from the electron gun 201 (emission unit)irradiates the entire first aperture plate 203 having a quadrangularopening by the illumination lens 202. At this point, the electron beam200 is shaped to a quadrangle. Then, after having passed through thefirst aperture plate 203, the electron beam 200 of a first apertureimage is projected onto the second aperture plate 206 by the projectionlens 204. The first aperture image on the second aperture plate 206 isdeflection-controlled by the deflector 205 so as to change the shape andsize of the beam to be variably shaped. After having passed through thesecond aperture plate 206, the electron beam 200 of a second apertureimage is focused by the objective lens 207 and deflected by the maindeflector 208 and the sub deflector 209, and reaches a desired positionon the target object 101 on the XY stage 105 which moves continuously.FIG. 1 shows the case of using a multiple stage deflector of two stagesof the main and sub deflectors for position deflection. In such a case,the main deflector 208 may deflect the electron beam 200 of the shotconcerned to a reference position of a subfield (SF), which is obtainedby further dividing the stripe region virtually, while following thestage movement, and the sub deflector 209 may deflect the beam of theshot concerned to each irradiation position in the SF.

FIG. 7 is an example of a graph showing a relation between an input dataamount and time of a buffer memory according to the first embodiment. InFIG. 7, the amount of input data of the buffer memory is represented bythe ordinate axis and time is represented by the abscissa axis. In thecase of memory control by a conventional OS, when data is read into thememory by the OS control, fragmentation may occur in the memory.Furthermore, if the memory capacity becomes insufficient, the OSperforms a swap-out operation by using the hard disk etc. Thereby, whendata conversion processing of writing data is performed in the systemside, the data read-out time becomes long, which makes the dataprocessing stopped temporarily. On the other hand, according to thefirst embodiment, since the memory control is performed in accordancewith an actual memory region 20 of the buffer memory 114 in the controlcomputer 110, it is possible to avoid producing fragmentation.Furthermore, according to the first embodiment, it is possible to avoidthat the amount of input data exceeds a specified amount (acceptableamount) of the actual memory region 20 of the buffer memory 114. Theusage rate of the buffer memory 114 according to the first embodimentfluctuates approximately between 80 and 90% Therefore, it is possible toavoid producing swapping out. Conseqently, when performing dataconversion processing by the writing data pressing unit 59, dataread-out can be completed in a short time, and therefore, stopping ofdata processing can be avoided. Data processing, which becomes time-outbecause read-out takes a long time due to swapping-out by a conventionalmethod, can be actually executed according to the first embodiment.

As described above, according to the first embodiment, fragmentation andswapping-out in a memory can be inhibited. As a result, stopping(deadlock) of data processing itself can be avoided, thereby preventingstopping of writing processing.

Second Embodiment

In the first embodiment, the memory region 20 of the buffer memory 114is divided into the large data size region 22 (A) and the small datasize region 24 (B), and data files to be stored therein aredistinguished from each other. On the other hand, in the secondembodiment, a method that can suppress at least swapping out by asimpler method will be described. The structure of the writing apparatusaccording to the second embodiment is the same as that of FIG. 1 exceptthat the dividing unit 50 and the region specifying unit 52 areunnecessary. The content of the second embodiment may be the same asthat of the first embodiment except what is particularly describedbelow.

FIG. 8 is a conceptual diagram showing a memory region of a buffermemory according to the second embodiment. The read unit 56 makes a setof data files (a cell pattern data file, a position data file, and alink file) for each frame region 12, and reads and stores it into thememory region 20 of the buffer memory 114. In the case of FIG. 8, thecell pattern data file (1), the position data file (1), and the linkfile (1) of the first frame region 12 are stored in order as a set (1)at the end side of the memory region 20. Then, next to the set (1), thecell pattern data file (2), the position data file (2), and the linkfile (2) of the second frame region 12 are stored as a set (2).Similarly, each set is stored in order.

The determination unit 54 determines whether it is possible to acquire acontinuous region, whose size is greater than or equal to the sizenecessary for storing a plurality of data files of the frame region 12concerned, in a specified region in the buffer memory 112. If thecontinuous region greater than or equal to the required size isinsufficient, a set of unnecessary data files which have already beenused is deleted by the deletion unit 58 as needed in order commencingfrom the frame region 12 that was read early. In the example of FIG. 8,if there is not sufficient remaining amount of the region for readingthe data file set (4) of the fourth frame region 12, the data file set(1) for the first frame region 12 is deleted first. When the continuousregion is still insufficient, the data file set (2) for the second frameregion 12 is deleted. Data reading and data deleting are performed untilit is determined by the determination unit 57 that data files for allthe frame regions have been stored.

According to the second embodiment, since data files for the same frameregion 12 are always stored and deleted as a set, it is possible toavoid storing at least one of the data files in a different region.Therefore, fragmentation hardly occurs. Moreover, since data exceeding aspecified amount (acceptable amount) of the memory is not stored, it isalso possible to avoid swapping out. Consequently, stopping of dataprocessing can be avoided.

Embodiments have been explained referring to concrete examples asdescribed above. However, the present invention is not limited to thesespecific examples.

While the apparatus configuration, control method, and the like notdirectly necessary for explaining the present invention are notdescribed, some or all of them may be suitably selected and used whenneeded. For example, although description of the configuration of acontrol unit for controlling the writing apparatus 100 is omitted, itshould be understood that some or all of the configuration of thecontrol unit is to be selected and used appropriately when necessary.

In addition, any other charged particle beam writing apparatus, writingmethod, and method of storing data in a buffer memory that includeelements of the present invention and that can be appropriately modifiedby those skilled in the art are included within the scope of the presentinvention.

Additional advantages and modification will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. A charged particle beam writing apparatuscomprising: a buffer memory configured to include a memory regioncapable of contemporarily storing writing data for a plurality of dataprocessing regions obtained by virtually dividing a writing region of atarget object to be written using a charged particle beam, whereinwriting data including a plurality of data files is temporarily storedfor each of the plurality of data processing regions; a dividing unitconfigured to divide the memory region of the buffer memory into a firstregion whose region size is large and a second region whose region sizeis smaller than the region size of the first region; a region specifyingunit configured to specify the memory region of the buffer memorywherein a data file in which pattern data of a cell pattern composed ofat least one figure to be written on the target object using the chargedparticle beam is defined has priority to be stored in the first regionand a data file in which position data indicating a position on thetarget object of writing the cell pattern using the charged particlebeam is defined is stored at least in the second region, with respect tothe plurality of data files for the each of the plurality of dataprocessing regions included in the writing data; a data processing unitconfigured to read the plurality of data files corresponding to the eachof the plurality of data processing regions from the buffer memory, andto perform data processing using the plurality of data files having beenread; and a writing unit configured to write a pattern on the targetobject with charged particle beams, in accordance with content of thedata processing, for the each of the plurality of data processingregions.
 2. The apparatus according to claim 1, wherein a thresholdvalue of the memory region for dividing the memory region into the firstregion and the second region is determined by using a ratio of filesizes of the plurality of data files.
 3. The apparatus according toclaim 1, wherein the memory region of the buffer memory is divided intotwo of the first region and the second region.
 4. The apparatusaccording to claim 1, wherein a position data file in which positiondata indicating a position of a cell pattern composed of at least onefigure is defined, a pattern data file in which pattern data of the cellpattern is defined, and a link file in which link information forlinking the position data and the pattern data being corresponding toeach other is defined are included in the plurality of data files. 5.The apparatus according to claim 1 further comprising: a firstdetermination unit configured to determine, with respect to the each ofthe plurality of data processing regions, whether a continuous emptyregion whose size is greater than or equal to a size necessary forstoring the plurality of data files for one of the plurality of dataprocessing regions can be acquired in a specified memory region in thebuffer memory.
 6. The apparatus according to claim 5 further comprising:a read unit configured to, for the each of the plurality of dataprocessing regions, respectively read and store the plurality of datafiles into a specified region in the memory region of the buffer memory.7. The apparatus according to claim 6 further comprising: a seconddetermination unit configured to determine whether storing file data hasbeen completed with respect to all of the plurality of data processingregions.
 8. The apparatus according to claim 7 further comprising: adeletion unit configured to delete an unnecessary data file which hasalready been used in the plurality of data files, as needed in ordercommencing from one of the plurality of data processing regions that wasread early.
 9. The apparatus according to claim 1, wherein a file sizeof the data file in which pattern data of the cell pattern composed ofat least one figure to be written on the target object using the chargedparticle beam is greater than a file size of the data file in whichposition data indicating the position on the target object of writingthe cell pattern using the charged particle beam.
 10. A method ofstoring data in a buffer memory comprising: dividing a memory region ofa buffer memory, which can contemporarily store writing data for aplurality of data processing regions obtained by virtually dividing awriting region of a target object to be written using a charged particlebeam, wherein writing data including a plurality of data files istemporarily stored for each of the plurality of data processing regions,into a first region whose region size is large and a second region whoseregion size is smaller than the region size of the first region;specifying the memory region of the buffer memory such that a data filein which pattern data of a cell pattern composed of at least one figureto be written on the target object using the charged particle beam isdefined has priority to be stored in the first region and a data file inwhich position data indicating a position on the target object ofwriting the cell pattern using the charged particle beam is defined isstored at least in the second region, with respect to the plurality ofdata files for the each of the plurality of data processing regionsincluded in the writing data; and storing, for the each of the pluralityof data processing regions, the plurality of data files respectively ina specified memory region in the memory region of the buffer memory. 11.The method according to claim 10 further comprising: determining, withrespect to the each of the plurality of data processing regions, whethera continuous empty region whose size is greater than or equal to a sizenecessary for storing the plurality of data files for one of theplurality of data processing regions can be acquired in the specifiedmemory region in the buffer memory.
 12. The method according to claim10, wherein a file size of the data file in which pattern data of thecell pattern composed of at least one figure to be written on the targetobject using the charged particle beam is greater than a file size ofthe data file in which position data indicating the position on thetarget object of writing the cell pattern using the charged particlebeam.